A person having skill in the art field which embraces electronic measuring apparatus for medical use will be aware that `Doppler` type velocimeters have been commercially available for some time. Such devices detect velocity and direction of the circulation of blood through a given vessel by exploiting the Doppler effect, but cannot be considered measuring devices in the strict sense, as no calibration is possible.
The Doppler devices in question process a signal rebounding off corpuscles in the blood when the vessel under examination is invested with a beam of ultrasonic frequencies emitted by a transducer. The signal produced is suitably converted and fed into an electro-mechanical transducer in such a way as to generate an audible signal which, in current practice, serves to assess the hydraulic state of a blood vessel as an aid to diagnosis. Diagnosis of this conventional type makes no use of any remotely-reproduced visual indication of the cross-section of the blood vessel, or of variations in cross-section that occur from one moment to another; such visual information would be of considerable assistance however, and, correlated to the acoustic signal, could provide a visual representation of the hydraulic behavior of an artery or a vein.
The object of the invention disclosed herein is to provide an instrument which, by utilizing the audio output signal from a Doppler velocimeter, provides:
an acoustic signal processed in such a way as to enhance the quality of the information to be interpreted;
a circular cross-section representation of `relative` changes with time of the effective cross-section of a column of blood through a blood vessel under examination, and of variation in the cross-section during heartbeat;
a proportional numerical read-out of the maximum and the minimum radius of the cross-section representation during heartbeat;
the facility of link-up to a printer or recorder that will document variations in radius of the relative cross-section over a given period of time.